The "would you really read through the code" argument against open source is old and tired. There is no good reason to trust crypto-related software with secret source. You may not personally audit the code, but if there is no source, nobody will, and you basically have to take the publisher at their word. The promise of crypto is that you can manage who you trust, but you can't do that with unauditable code.

No, but a trusted expert may read through hundreds of thousands of lines of code and publish their findings in an article.